Many medicament delivery devices on the market today are arranged with a number of features that facilitate the use of the device because today's devices are more and more intended to be handled by the patients themselves. The added functionality may be an advantage when the medicament delivery devices comprise injection needles since many patients feel uncomfortable seeing the needle and also feel reluctant regarding penetration of the needle. In that respect, added functionality may include features such as automatic penetration mechanisms as well as automatic injection mechanisms.
Many medicament delivery devices that are arranged with automatic features and functions are often also arranged with some sort of actuation member that is operated by a user either indirectly when pressing the device against a dose delivery site or directly by operating an activation button on the device, such as at the distal end thereof.
Document WO 2012/105898 discloses an activating mechanism comprising an actuator in the form of a button protruding through the distal end of the housing part. The actuator is arranged to act on an actuator member comprised in a power unit of the device. The actuator member is arranged as a ring-shaped element that can be moved axially by the actuator. In one position, the actuator member locks movement of holding elements that are arranged to interact and hold a plunger rod in a tensioned state by a force member. The actuator may then move the actuator member to a release position where the holding elements may be moved out of engagement with the plunger rod, whereby the latter is free to move in the proximal direction by the force member, thereby enabling delivery of a dose of medicament.
The function of the power unit of WO 2012/105898 has proven to work in most instances. However, in some cases when the device has been accidentally dropped on a hard surface such as a table, a floor or the ground, impact forces may cause the actuator member to move from the locking position to the release position, thereby activating the device such that a dose is delivered unintentionally.
The dose is then wasted. If the device is a single-use device, then the device has to be discarded without having delivered any medicament to the patient and a new device has to be obtained. Even if the device is re-usable, it has to be reloaded in order to deliver a new dose. Both obtaining a new device or reloading a device is time-consuming and causes stress to a patient, especially in urgent situations.
There is thus a demand for devices having an increased functionality for minimizing the risk of activation after accidental drops and other types of accidental impacts.